Trisodium phosphate dodecahydrate flash cooling crystallization system

Abstract

The utility model discloses a kind of dodecahydrate trisodium phosphate flash cooling crystallization systems, sodium phosphate solution incoming pipe outlet is connected with the hot side entrance of array tube heat exchanger, and the hot side outlet of array tube heat exchanger is connected with the feed inlet of primary flash crystallizer;Primary flash lower cylinder circulation outlet is connected with upper cylinder circulation inlet by primary flash circulating pump;The crystal slurry outlet of primary flash crystallizer is connected with the circulation pipe of secondary flash crystallizer by primary flash material transfer pump;The crystal slurry outlet of secondary flash crystallizer is connected with thickener by secondary flash material transfer pump, and thickener overflow is connected with array tube heat exchanger cold side;Thickener bottom outlet is connected with centrifuge, and centrifugal solid phase connects product chute;Centrifugal liquid phase outlet is connected with mother liquor tank, and mother liquor tank outlet is connected with secondary flash crystallizer circulation pipe by mother liquor pump.The system is low in energy consumption, the obtained crystallization product granularity is uniform, high in purity, reduces waste liquid treatment capacity, realizes the recycling of resources, and improves economic benefit.

Description

Technical Field

[0001] This utility model relates to the treatment of electrolyte waste liquid, and more particularly to a flash evaporation and cooling crystallization system for trisodium dodecahydrate, belonging to the field of resource comprehensive utilization technology. Background Technology

[0002] Trisodium phosphate dodecahydrate is an important inorganic compound, a colorless rod-shaped crystal at room temperature, readily soluble in water, and its aqueous solution is strongly alkaline. The phosphate and sodium ions in its molecule endow it with excellent complexing, dispersing, and water softening properties, thus making it widely used in detergents, metal surface treatment, food processing, and water treatment. In recent years, with increasingly stringent global environmental regulations and the demand for industrial upgrading, the application scenarios and production processes of this compound are facing new opportunities and challenges.

[0003] In terms of traditional production processes, the production of trisodium dodecahydrate mostly adopts the traditional extraction phosphoric acid method and soda ash neutralization method, which are energy-intensive, complex and difficult to handle. In addition, the product of sodium dodecahydrate has uneven particle size, low purity, and low utilization value.

[0004] Chinese utility model patent with publication number CN220780266U discloses a reaction device for the production of disodium hydrogen phosphite, including a mounting base plate, a placement tank, a water storage cylinder, and a water bath evaporator. This device controls the precision of salt production by feeding materials. It is small-scale and cannot produce continuously. In addition, the disodium hydrogen phosphite produced by this device is less valuable than trisodium phosphate dodecahydrate, bringing less value to enterprises and causing a certain waste of resources. Utility Model Content

[0005] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, and such simplifications or omissions should not be construed as limiting the scope of the present invention.

[0006] In view of the problems existing in the above and / or prior art, this utility model is proposed.

[0007] The purpose of this invention is to overcome the problems existing in the prior art and provide a flash cooling crystallization system for trisodium dodecahydrate, which has low energy consumption, produces trisodium dodecahydrate crystals with uniform particle size and high purity, reduces the amount of waste liquid to be treated, realizes resource recycling, and improves economic efficiency.

[0008] To solve the above technical problems, this utility model provides a flash cooling crystallization system for trisodium phosphate dodecahydrate, comprising a sodium phosphate solution feed pipe, the outlet of which is connected to the hot-side inlet of a tube heat exchanger, and the hot-side outlet of the tube heat exchanger connected to the feed inlet of a first-stage flash crystallizer; the lower cylinder circulation outlet of the first-stage flash crystallizer is connected to the upper cylinder circulation inlet via a first-stage flash circulation pump; the crystal slurry outlet of the first-stage flash crystallizer is connected to the circulation pipe of a second-stage flash crystallizer via a first-stage flash transfer pump; the crystal slurry outlet of the second-stage flash crystallizer is connected to the inlet of a thickener via a second-stage flash transfer pump, and the overflow of the thickener is connected to the cold side of the tube heat exchanger; the bottom outlet of the thickener is connected to the inlet of a centrifuge, and the solid phase outlet of the centrifuge is connected to a product chute; the liquid phase outlet of the centrifuge is connected to the inlet of a mother liquor tank, and the outlet of the mother liquor tank is connected to the circulation pipe of the second-stage flash crystallizer via a mother liquor pump.

[0009] As an improvement of this utility model, the overflow port of the thickener is connected to the top inlet of the discharge tank; the lower outlet of the discharge tank is connected to the cold side inlet of the tube heat exchanger through the discharge pump, and the cold side outlet of the tube heat exchanger is connected to the flash clear liquid discharge pipe.

[0010] As a further improvement of this utility model, the upper overflow port and the bottom vent of the discharge tank are also connected to the inlet of the mother liquor tank.

[0011] As a further improvement of this utility model, the lower cylinder circulation outlet of the secondary flash crystallizer is connected to the upper cylinder circulation inlet of the secondary flash crystallizer through a secondary flash circulation pump and a secondary flash circulation pipe; the outlet pipe of the mother liquor pump is connected to the inlet pipe of the secondary flash circulation pump.

[0012] As a further improvement of this utility model, the outlet of the secondary flash transfer pump is also connected to the reflux port of the upper cylinder of the secondary flash crystallizer through a reflux pipe.

[0013] As a further improvement of this utility model, the top exhaust port of the first-stage flash crystallizer is connected to the shell-side inlet of the first-stage flash condenser, the shell-side outlet of the first-stage flash condenser is connected to the middle inlet of the first-stage gas-liquid separator, the top exhaust port of the first-stage gas-liquid separator is connected to the first-stage vacuum pump group; the bottom drain port of the first-stage gas-liquid separator is connected to the inlet liquid seal pipe of the first-stage flash condensate tank, and the outlet of the first-stage flash condensate tank is connected to the condensate recovery system through the first-stage flash condensate pump.

[0014] As a further improvement of this utility model, the top flash vapor outlet of the secondary flash crystallizer is connected to the shell-side inlet of the secondary flash condenser, the shell-side outlet of the secondary flash condenser is connected to the inlet of the secondary gas-liquid separator, and the top exhaust port of the secondary gas-liquid separator is connected to the secondary vacuum pump unit.

[0015] As a further improvement of this utility model, the outlet of the refrigerant water tank is connected to the refrigerant water inlet of the refrigeration unit through a refrigerant water pump, the refrigerant water outlet of the refrigeration unit is connected to the tube-side inlet of the secondary flash condenser, and the tube-side outlet of the secondary flash condenser is connected to the top return port of the refrigerant water tank.

[0016] As a further improvement of this utility model, the bottom drain port of the secondary gas-liquid separator and the shell-side drain port of the secondary flash condenser are respectively connected to the inlet liquid seal pipe of the secondary flash condensate tank, and the outlet of the secondary flash condensate tank is connected to the condensate recovery system through the secondary flash condensate pump.

[0017] As a further improvement of this utility model, the feature is that: a filter screen structure is provided in the middle of the lower cylinder of the first-stage flash crystallizer, and a spiral conveying device is provided at the bottom.

[0018] Compared with existing technologies, this utility model achieves the following beneficial effects: 1. The adoption of a two-stage flash evaporation cooling crystallization system simplifies the entire process and enables continuous, uninterrupted production. Through precise gradient adjustment of the system pressure and optimization of crystallization kinetics, the two-stage flash evaporation crystallization process allows the trisodium dodecahydrate product to form larger, more saturated hexagonal prism crystals with more uniform particle size and a purity ≥98%, meeting the first-class standard in "HGT 2517-2009 Industrial Trisodium Phosphate," thus possessing higher market value.

[0019] 2. The sodium phosphate-containing wastewater is treated with a two-stage flash evaporation and cooling crystallization process to obtain the product trisodium phosphate dodecahydrate. This process converts the sodium salt in the wastewater into industrial salt, which not only saves the cost of treating the sodium phosphate-containing wastewater, but also produces higher-value by-products, increases revenue, meets green manufacturing standards, and emphasizes environmental friendliness and functional refinement. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. The drawings are provided for reference and illustration only and are not intended to limit this utility model. Wherein:

[0021] Figure 1 This is a flowchart of the flash cooling crystallization system for trisodium dodecahydrate of this utility model;

[0022] In the diagram: 1. Shell and tube heat exchanger; 2. First-stage flash crystallizer; 3. First-stage flash condenser; 4. First-stage gas-liquid separator; 5. First-stage flash condensate tank; 6. First-stage vacuum pump unit; 7. Second-stage flash crystallizer; 8. Thickener; 9. Centrifuge; 10. Discharge tank; 11. Mother liquor tank; 12. Second-stage flash condenser; 13. Second-stage gas-liquid separator; 14. Second-stage vacuum pump unit; 15. Second-stage flash condensate tank; 16. Refrigeration unit; 17. Refrigerant water tank;

[0023] B1. First-stage flash condensate pump; B2. First-stage flash circulation pump; B3. First-stage flash transfer pump; B4. Second-stage flash circulation pump; B5. Second-stage flash transfer pump; B6. Mother liquor pump; B7. Discharge pump; B8. Second-stage flash condensate pump; B9. Refrigerant water pump;

[0024] G1. Sodium phosphate solution feed pipe; G2. Flash evaporation clear liquid discharge pipe; G3. Cooling water inlet pipe; G4. Cooling water outlet pipe; G5. Condensate collection pipe; G6. Product chute. Detailed Implementation

[0025] In the following description of this utility model, the terms "upper", "lower", "front", "rear", "left", "right", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and do not mean that the device must have a specific orientation.

[0026] To make the technical means, creative features, achieved objectives and effects of this utility model easier to understand, the present utility model will be further described below with reference to specific illustrations. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0028] like Figure 1 As shown, the flash cooling crystallization system of trisodium phosphate dodecahydrate of this utility model includes a shell and tube heat exchanger 1, a first-stage flash crystallizer 2, a first-stage flash condenser 3, a first-stage gas-liquid separator 4, a first-stage flash condensate tank 5, a first-stage vacuum pump set 6, a second-stage flash crystallizer 7, a thickener 8, a centrifuge 9, a discharge tank 10, a mother liquor tank 11, a second-stage flash condenser 12, a second-stage gas-liquid separator 13, a second-stage vacuum pump set 14, a second-stage flash condensate tank 15, a refrigeration unit 16, and a refrigerant water tank 17.

[0029] The outlet of the sodium phosphate solution feed pipe G1 is connected to the hot side inlet of the tube heat exchanger 1. The hot side outlet of the tube heat exchanger 1 is connected to the feed inlet of the first-stage flash crystallizer 2. The lower cylinder circulation outlet of the first-stage flash crystallizer 2 is connected to the upper cylinder circulation inlet of the first-stage flash crystallizer 2 through the first-stage flash circulation pump B2 and the first-stage flash circulation pipe.

[0030] The top vent of the first-stage flash crystallizer 2 is connected to the shell-side inlet of the first-stage flash condenser 3. The shell-side outlet of the first-stage flash condenser 3 is connected to the middle inlet of the first-stage gas-liquid separator 4. The top vent of the first-stage gas-liquid separator 4 is connected to the first-stage vacuum pump group 6. The bottom drain of the first-stage gas-liquid separator 4 is connected to the inlet liquid seal pipe of the first-stage flash condensate tank 5. The bottom outlet of the condensate tank 5 is connected to the inlet of the first-stage flash condensate pump B1. The outlet of the first-stage flash condensate pump B1 is connected to the condensate recovery system through the condensate collection pipe G5. The top vent of the condensate tank 5 is connected to the shell-side exhaust port of the first-stage flash condenser 3. The bottom drain of the shell-side of the first-stage flash condenser 3 is connected to the inlet of the condensate tank 5. The tube-side inlet of the first-stage flash condenser 3 is connected to the cooling water inlet pipe G3. The tube-side outlet of the first-stage flash condenser 3 is connected to the cooling water outlet pipe G4.

[0031] The bottom slurry outlet of the primary flash crystallizer 2 is connected to the inlet of the primary flash transfer pump B3. The outlet of the primary flash transfer pump B3 is connected to the middle inlet of the secondary flash circulation pipe. The upper end of the secondary flash circulation pipe is connected to the upper cylinder circulation inlet of the secondary flash crystallizer 7. The lower end of the secondary flash circulation pipe is connected to the outlet of the secondary flash circulation pump B4. The inlet pipe of the secondary flash circulation pump B4 is connected to the lower cylinder circulation outlet of the secondary flash crystallizer 7.

[0032] The secondary flash crystallizer 7 is an Oslo crystallizer. Its bottom crystal slurry outlet is connected to the inlet of the secondary flash transfer pump B5. The outlet pipe of the secondary flash transfer pump B5 is connected to the upper cylinder reflux port of the secondary flash crystallizer 7 and the top inlet of the thickener 8. The bottom outlet of the thickener 8 is connected to the inlet of the centrifuge 9. The solid phase outlet of the centrifuge 9 is connected to the product chute G6.

[0033] The upper overflow port of the thickener 8 is connected to the top inlet of the discharge tank 10. The upper side wall overflow port and the bottom vent of the discharge tank 10 are connected to the inlet of the mother liquor tank 11, respectively. The liquid phase outlet of the centrifuge 9 is also connected to the inlet of the mother liquor tank 11. The outlet of the mother liquor tank 11 is connected to the inlet of the mother liquor pump B6. The outlet pipe of the mother liquor pump B6 is connected to the inlet pipe of the secondary flash circulation pump B4.

[0034] The lower outlet of the discharge tank 10 is connected to the inlet of the discharge pump B7, the outlet pipe of the discharge pump B7 is connected to the cold side inlet of the tube heat exchanger 1, and the cold side outlet of the tube heat exchanger 1 is connected to the flash clear liquid discharge pipe G2.

[0035] The top flash vapor outlet of the secondary flash crystallizer 7 is connected to the shell-side inlet of the secondary flash condenser 12. The shell-side outlet of the secondary flash condenser 12 is connected to the middle inlet of the secondary gas-liquid separator 13. The top exhaust port of the secondary gas-liquid separator 13 is connected to the secondary vacuum pump group 14. The bottom drain port of the secondary gas-liquid separator 13 is connected to the inlet liquid seal pipe of the secondary flash condensate tank 15. The shell-side condensate outlet of the secondary flash condenser 12 is also connected to the inlet liquid seal pipe of the secondary flash condensate tank 15. The top exhaust port of the secondary flash condensate tank 15 is connected to the shell-side exhaust port of the secondary flash condenser 12. The bottom drain port of the secondary flash condensate tank 15 is connected to the inlet of the secondary flash condensate pump B8. The outlet of the secondary flash condensate pump B8 is connected to the condensate recovery system through the condensate collection pipe G5.

[0036] The bottom outlet of the refrigerant water tank 17 is connected to the inlet of the refrigerant water pump B9. The outlet of the refrigerant water pump B9 is connected to the refrigerant water inlet of the refrigeration unit 16. The refrigerant water outlet of the refrigeration unit 16 is connected to the tube-side inlet of the secondary flash condenser 12. The tube-side outlet of the secondary flash condenser 12 is connected to the top return port of the refrigerant water tank 17. The cooling water inlet of the refrigeration unit 16 is connected to the cooling water inlet pipe G3, and the cooling water outlet of the refrigeration unit 16 is connected to the cooling water outlet pipe G4.

[0037] The lower cylinder of the first-stage flash crystallizer 2 is equipped with a filter screen structure in the middle and a spiral conveyor at the bottom. Through the synergistic effect of the middle filter screen and the bottom spiral conveyor, precise control of salt particle size is achieved, enabling graded screening: the filter screen dynamically traps the crystal slurry, allowing only crystals with the required particle size to sink to the bottom, while fine particles are returned to the evaporation zone by the first-stage flash circulation pump B2 for secondary growth. This avoids the particle size distribution dispersion problem caused by "fine crystal entrainment" and allows for the formation of denser crystals with better monodispersity in the second-stage flash crystallizer 7 under the guidance of stable seed crystals. It also achieves directional and stable flow: the spiral conveyor transports the bottom crystals to the second-stage flash crystallizer 7 at a constant rate, avoiding supersaturation jumps caused by feed fluctuations, continuously ensuring the steady state of process parameters, and providing a uniform seed base for secondary crystal growth, ensuring a dynamic balance between the crystal nucleus growth rate and solution supersaturation.

[0038] The secondary flash crystallizer 7 adopts a "directed seeding and dual-zone dynamic balance" design. The stably added seed crystals provide a uniform nucleation substrate for the solution, inhibiting disordered spontaneous nucleation, promoting directional deposition of solute, and improving the uniformity of crystal size. At the same time, the top of the secondary flash crystallizer is equipped with a dual-blade variable frequency stirrer. The upper blade is in the evaporation zone to eliminate explosive nucleation caused by local supersaturation. The lower blade is in the bottom discharge zone to gently stir and turn the salt bed, avoiding excessive particles that could cause blockage in the bottom discharge area.

[0039] A two-stage flash evaporation cooling crystallization method is adopted, utilizing the solubility of trisodium phosphate dodecahydrate to achieve gradient cooling. The evaporation temperature is controlled by precise pressure adjustment inside the flash crystallizer. The first-stage flash evaporation temperature is higher than the second-stage flash evaporation temperature. The first-stage flash evaporation is used to suppress the explosive release of supersaturated evaporated material. The second-stage flash evaporation intensity is lower than the first-stage flash evaporation, providing a mild environment for crystal growth. The crystal particle size distribution is concentrated, and the product crystal particles are larger, fuller, and more stable in morphology.

[0040] The centrifugal mother liquor is recycled in a closed loop. By returning the mother liquor and entrained microcrystals after solid-liquid separation to the crystallizer, the concentration of crystal nuclei is replenished and the fine crystals are re-dissolved and regenerated. The returned microcrystals serve as seed crystals. At the same time, it can suppress spontaneous nucleation caused by solution oversaturation and overload, and maintain a constant crystal growth rate.

[0041] The sodium phosphate solution from the sodium phosphate solution feed pipe G1 is at a temperature greater than 80°C and has a density of 1100 kg / m³. After entering the hot side of the tube heat exchanger 1, it is cooled down to 50°C. The cold source used on the cold side of the tube heat exchanger 1 is the 25°C flash evaporated liquid delivered by the discharge pump B7. After heat exchange, the flash evaporated liquid is discharged through the flash evaporated liquid discharge pipe G2.

[0042] Sodium phosphate solution cooled to 50°C enters the first-stage flash crystallizer 2. After the liquid level submerges the circulation pipe, the first-stage flash circulation pump B2 is started to circulate the solution. Once the liquid surface begins to churn as seen through the sight glass, the first-stage vacuum pump group 6 is started to evacuate the system, controlling the negative pressure inside the first-stage flash crystallizer 2 at -90 kPa. The secondary steam generated by flash evaporation enters the hot side (shell side) of the first-stage flash condenser 3. Circulating cooling water is introduced into the cold side (tube side) of the first-stage flash condenser 3 to condense the secondary steam. The condensed steam then enters the first-stage gas-liquid separator 4 for separation. Non-condensable gases are extracted from the top of the first-stage gas-liquid separator 4 by the first-stage vacuum pump group 6 and discharged into the atmosphere.

[0043] The condensate discharged from the bottom of the first-stage gas-liquid separator 4 enters the first-stage flash condensate tank 5 for collection, is then pumped out by the first-stage flash condensate pump B1 and enters the condensate recycling system through the condensate collection pipe G5.

[0044] The temperature inside the first-stage flash crystallizer 2 is adjusted by precisely controlling the internal negative pressure of the system until it reaches 45°C. At this point, trisodium phosphate dodecahydrate begins to precipitate and is transferred to the second-stage flash crystallizer 7 via the first-stage flash transfer pump B3. During this process, the second-stage flash circulation pump B2 continues to operate, ensuring a sufficient liquid level in the first-stage flash crystallizer 2. Once the liquid level in the second-stage flash crystallizer 7 reaches one-third of the upper cylinder, the refrigerant water pump B9 is activated, drawing refrigerant water from the refrigerant water tank 17 and sending it to the evaporator of the refrigeration unit 16 for cooling. After passing through the tubes of the second-stage flash condenser 12, the refrigerant water returns to the refrigerant water tank 17 for circulation. Then, the refrigeration unit 16 is activated to lower the temperature of the refrigerant water sent to the tubes of the second-stage flash condenser 12 to 10°C, ensuring that the heat carried by the flashed secondary vapor is removed. The cooling unit of the refrigeration unit 16 uses circulating cooling water to remove the heat.

[0045] After the refrigeration unit 16 is running normally, the secondary vacuum pump unit 14 is turned on. This pump unit is composed of a water ring vacuum pump and a Roots vacuum pump. The secondary vacuum pump unit 14 controls the negative pressure in the secondary flash crystallizer 7 at -98KPa and precisely controls the temperature of the secondary flash system at 25℃. At this temperature, the precipitation rate of trisodium phosphate dodecahydrate is the highest. The secondary flash circulation pump B4 provides the circulation power. Finally, the crystal slurry discharged from the bottom of the secondary flash crystallizer 7 is transported to the thickener 8 through the secondary flash transfer pump B5. The thickener 8 is equipped with a frame agitator, which can make the crystal slurry achieve solid-liquid stratification, allowing the particulate material to fall into the lower cone. Then, it flows into the centrifuge 9 by gravity. The centrifugal force of the centrifuge 9 separates the crystal slurry material into solid and liquid. The solid is discharged from the solid phase outlet through the product chute G6 and packaged in ton bags.

[0046] The clear liquid at the top of the thickener 8 overflows into the clear liquid tank 10. The material at the bottom of the clear liquid tank 10 is sent to the tube side of the tube heat exchanger 1 through the discharge pump B7 to cool the sodium phosphate solution. The temperature of the clear liquid after heat exchange is 50°C, and it is discharged out of the system through the flash clear liquid discharge pipe G2.

[0047] The mother liquor overflowing from the top of the clear liquid tank 10 enters the mother liquor tank 11 for collection. The mother liquor discharged from the liquid phase of the centrifuge 9 also enters the mother liquor tank 11 for collection. It is then pumped out by the mother liquor pump B6 and injected into the circulation pipe of the secondary flash crystallizer 7, so that it can return to the system for circulation.

[0048] The secondary steam discharged from the top of the secondary flash crystallizer 7 enters the shell side of the secondary flash condenser 12 for condensation, and then enters the secondary gas-liquid separator 13 for separation. The non-condensable gas is extracted from the top of the secondary gas-liquid separator 13 by the secondary vacuum pump group 14 and discharged into the atmosphere.

[0049] The condensate discharged from the bottom of the secondary gas-liquid separator 13 is collected in the secondary flash condensate tank 15, and then pumped out by the secondary flash condensate pump B8 and enters the condensate recycling system through the condensate collection pipe G5.

[0050] This system utilizes a primary vacuum pump group 6 and a secondary vacuum pump group 14 to achieve precise negative pressure control and feed flow regulation for the primary flash crystallizer 2 and the secondary flash crystallizer 7, thereby obtaining relatively pure trisodium phosphate dodecahydrate. A certain number of seed crystals are guaranteed in a suitable area through a specific device inside the crystallizer. Moreover, trisodium phosphate dodecahydrate has a high recovery value, which can compensate for part of the cost of wastewater discharge and improve environmental and economic benefits.

[0051] Due to the many uncertainties in the system, this system is equipped with a refrigeration unit 16, a first-stage flash condenser 3, and a second-stage flash condenser 12 to ensure that the negative pressure inside the crystallizer can fully meet the system requirements, ensure continuous and stable operation within the system, achieve production targets, and guarantee economic benefits.

[0052] The above description is merely a preferred embodiment of the present utility model, showing and describing the basic principles, main features, and advantages of the present utility model. It is not intended to limit the scope of patent protection of the present utility model. Those skilled in the art should understand that the present utility model is not limited to the above embodiments. In addition to the above embodiments, the present utility model may have other implementations without departing from the spirit and scope of the present utility model. Various changes and improvements to the present utility model are also possible. All technical solutions formed by equivalent substitutions or equivalent transformations fall within the scope of protection claimed by the present utility model. The scope of protection claimed by the present utility model is defined by the appended claims and their equivalents. Technical features not described in the present utility model can be implemented by or using existing technology, and will not be elaborated here.

Claims

1. A flash cooling crystallization system for trisodium phosphate dodecahydrate, comprising a sodium phosphate solution feed pipe (G1), characterized in that, The outlet of the sodium phosphate solution feed pipe (G1) is connected to the hot-side inlet of the tube heat exchanger (1), and the hot-side outlet of the tube heat exchanger (1) is connected to the feed inlet of the first-stage flash crystallizer (2); the lower cylinder circulation outlet of the first-stage flash crystallizer (2) is connected to the upper cylinder circulation inlet through the first-stage flash circulation pump (B2); the crystal slurry outlet of the first-stage flash crystallizer (2) is connected to the circulation pipe of the second-stage flash crystallizer (7) through the first-stage flash transfer pump (B3); the crystal slurry outlet of the second-stage flash crystallizer (7) is connected to the circulation pipe of the second-stage flash crystallizer (7). The slurry outlet is connected to the inlet of the thickener (8) via a secondary flash transfer pump (B5), and the overflow of the thickener (8) is connected to the cold side of the tube heat exchanger (1). The bottom outlet of the thickener (8) is connected to the inlet of the centrifuge (9), and the solid phase outlet of the centrifuge (9) is connected to the product chute (G6). The liquid phase outlet of the centrifuge (9) is connected to the inlet of the mother liquor tank (11), and the outlet of the mother liquor tank (11) is connected to the circulation pipe of the secondary flash crystallizer (7) via the mother liquor pump (B6).

2. The flash cooling crystallization system for trisodium dodecahydrate according to claim 1, characterized in that: The overflow port of the thickener (8) is connected to the top inlet of the discharge tank (10); the lower outlet of the discharge tank (10) is connected to the cold side inlet of the tube heat exchanger (1) through the discharge pump (B7), and the cold side outlet of the tube heat exchanger (1) is connected to the flash clear liquid discharge pipe (G2).

3. The flash cooling crystallization system for trisodium dodecahydrate according to claim 2, characterized in that: The upper overflow port and the bottom vent of the discharge tank (10) are also connected to the inlet of the mother liquor tank (11).

4. The flash cooling crystallization system for trisodium dodecahydrate according to claim 1, characterized in that: The lower cylinder circulation outlet of the secondary flash crystallizer (7) is connected to the upper cylinder circulation inlet of the secondary flash crystallizer (7) through the secondary flash circulation pump (B4) and the secondary flash circulation pipe; the outlet pipe of the mother liquor pump (B6) is connected to the inlet pipe of the secondary flash circulation pump (B4).

5. The flash cooling crystallization system for trisodium dodecahydrate according to claim 1, characterized in that: The outlet of the secondary flash transfer pump (B5) is also connected to the reflux port of the upper cylinder of the secondary flash crystallizer (7) via a reflux pipe.

6. The flash cooling crystallization system for trisodium dodecahydrate according to claim 1, characterized in that: The top exhaust port of the first-stage flash crystallizer (2) is connected to the shell-side inlet of the first-stage flash condenser (3), the shell-side outlet of the first-stage flash condenser (3) is connected to the middle inlet of the first-stage gas-liquid separator (4), the top exhaust port of the first-stage gas-liquid separator (4) is connected to the first-stage vacuum pump group (6); the bottom drain port of the first-stage gas-liquid separator (4) is connected to the inlet liquid seal pipe of the first-stage flash condensate tank (5), and the outlet of the first-stage flash condensate tank (5) is connected to the condensate recovery system through the first-stage flash condensate pump (B1).

7. The flash cooling crystallization system for trisodium dodecahydrate according to claim 1, characterized in that: The top flash outlet of the secondary flash crystallizer (7) is connected to the shell-side inlet of the secondary flash condenser (12), the shell-side outlet of the secondary flash condenser (12) is connected to the inlet of the secondary gas-liquid separator (13), and the top exhaust port of the secondary gas-liquid separator (13) is connected to the secondary vacuum pump group (14).

8. The flash cooling crystallization system for trisodium dodecahydrate according to claim 7, characterized in that: The outlet of the refrigerant water tank (17) is connected to the refrigerant water inlet of the refrigeration unit (16) via the refrigerant water pump (B9). The refrigerant water outlet of the refrigeration unit (16) is connected to the tube-side inlet of the secondary flash condenser (12). The tube-side outlet of the secondary flash condenser (12) is connected to the top return port of the refrigerant water tank (17).

9. The flash cooling crystallization system for trisodium dodecahydrate according to claim 7, characterized in that: The bottom drain of the secondary gas-liquid separator (13) and the shell drain of the secondary flash condenser (12) are respectively connected to the inlet liquid seal pipe of the secondary flash condensate tank (15). The outlet of the secondary flash condensate tank (15) is connected to the condensate recovery system through the secondary flash condensate pump (B8).

10. The flash cooling crystallization system for trisodium dodecahydrate according to any one of claims 1 to 9, characterized in that: The lower cylinder of the first-stage flash crystallizer (2) is equipped with a filter screen structure and a spiral conveyor at the bottom.

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